open

# File activerecord/lib/active_record/connection_adapters/schema_cache.rb, line 468
        def open(filename)
          FileUtils.mkdir_p(File.dirname(filename))

          File.atomic_write(filename) do |file|
            if File.extname(filename) == ".gz"
              zipper = Zlib::GzipWriter.new file
              zipper.mtime = 0
              yield zipper
              zipper.flush
              zipper.close
            else
              yield file
            end
          end
        end